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Adrienne Owens

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Bluetooth audio splinters -- PC, consumer divide may herald incompatible products

San Jose, Calif. - Computer and consumer engineers are taking separate paths to delivering audio over Bluetooth, raising the possibility of incompatible wireless MP3 players, headsets and speakers. The split comes as Bluetooth gains traction in its core market of cellular handsets and as it marshals forces for a next-generation spec that could deliver megabit data rates along with multimedia.

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A handful of top consumer companies-including Matsushita, Philips, Sony and Toshiba-have defined a low-cost means for streaming audio to Bluetooth headsets, with plans to roll out products in 2004. At the same time, Microsoft and a group of unnamed OEMs are hammering out a different approach, based on the Internet Protocol (IP), to implement on the PC.

"We may see multiple standards existing," said J. Eric Janson, vice president of marketing for Cambridge Silicon Radio (Cambridge, England), one of the top Bluetooth chip suppliers. "I'd sooner everyone go in one direction so we can optimize around that and take the cost out of it, but I'm not sure that's realistic at this point."

In contrast to Microsoft's IP approach, companies within the consumer audio/video working group of the Bluetooth Special Interest Group (SIG) have defined a mechanism for streaming audio over Bluetooth using the Real Time Protocol established by the Internet Engineering Task Force.

"At this point there is a controversy as to whether IP is cost-effective for simple devices like headphones," said Tsuyoshi Okada, a staff engineer in the wireless group at Matsushita Electric Industrial Co. (Osaka, Japan). "So far we haven't found a need for an IP address on such devices."

Matsushita and others in the A/V working group are preparing MP3 players, headsets and speakers using the current 723-kbit/second Bluetooth version 1.2 spec and an advanced audio distribution profile (A2DP) defined by the SIG in May. Some of the companies are in talks with Microsoft to find ways to bridge the two efforts. "We want to make sure our headsets interoperate with PCs," said Okada.

The issue for Microsoft is audio quality, particularly in an environment of multiple Bluetooth devices. Wireless keyboards, mice and other 2.4-GHz gadgets could generate interference that might result in crackling speakers when PCs stream audio over Bluetooth. A2DP is essentially a point-to-point spec that does not take that scenario into account, said Mike Foley, a wireless architect at Microsoft Corp. "We're working with OEMs to come up with a solution," Foley said. "It's a very important issue."

Microsoft's ad hoc effort is defining a way to implement audio over IP that would span multiple wireless networks, including Bluetooth and Wi-Fi. Microsoft engineers are developing a straw man proposal that they will share with a select group of digital audio engineers in hopes that it could become a formal proposal to be shared with the industry. Foley would not name companies involved in the effort or say when the work will be finished.

"There are a lot of consumer companies that want to get products out, and if they wait for Microsoft, it will delay them," said Jennifer Bray, who tracks standards for Cambridge Silicon Radio (CSR).

Microsoft elected not to include native support for Bluetooth in Windows XP, though the company did ship in September an add-on pack with a Bluetooth application programming interface. Going forward, Microsoft has kicked off an effort to define an umbrella set of APIs in its Winsock framework. Under that framework, which will probably be built into Longhorn, the next generation of Windows, developers would write to Winsock and Windows would determine what services are passed over what networks.

Apple Computer Inc. has taken a different approach, building Bluetooth support into its OS X and into its current series of Powerbook notebooks. David Russell, director of product marketing for wireless and notebooks at Apple, urged developers at the Bluetooth Americas conference here last week to accelerate adoption by making Bluetooth easier to set up and use.

Russell would not comment on widespread reports at the conference that the next version of Apple's iPod MP3 player will use Bluetooth. He poured cold water on the idea of using Bluetooth to download music to a system that currently uses USB or Firewire interfaces for that function. However, asked whether Bluetooth could be used to stream music to car, headset or home speakers, Russell said, "That might be something to consider."

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Indeed, at the conference, consumer audio devices were seen as the next likely target for Bluetooth, for which some 75 million chip sets will ship this year, mostly for GSM phones in Europe and Asia.

In separate presentations, chip and software vendors indicated several challenges to delivering music over Bluetooth. Systems will need sub-band coding to efficiently move MP3, Windows Media or other codec files in a simple way to a headset or speaker. Headsets should have 80 milliseconds or less latency to stay in synch with video from a TV. A Broadcom manager said upcoming megabit versions of Bluetooth will be required to eliminate the need for large and expensive buffers in wireless headsets. Janson of CSR noted that vendors also will have to work out ways to protect copyrights for wireless music, another thorny issue.

Megabit spec ready

The audio debate comes as the Bluetooth SIG is setting up a new road map committee to solicit broad market input on directions and timing for the next revisions of the short-range wireless link. The committee could help the SIG get control of an expanding list of applications, and software profiles to go with them, as well as proposals for low- and high-end versions of the spec that could clash with 802.11, ultrawideband and Zigbee networks.

"The SIG has become a dumping ground for profiles," said Seamus McAteer, an analyst with Zelos Group (San Francisco) who follows Bluetooth.

The SIG has already queued up work on a number of advancements for the technology that could find their way into a next major release of Bluetooth. Perhaps the most prominent is a so-called medium-rate version that will offer effective data rates of 1.4 and 2.1 Mbits/s based on a switch to four- or eight-level phase-shift-keying modulation, respectively. The technology could be used for bandwidth-hungry applications such as digital cameras and MP3 players. It could also be used to lower power consumption by as much as two-thirds for devices such as wireless cellular headsets.

Cambridge Silicon Radio and Silicon Wave (San Diego) have jointly tested products that conform to the still-unofficial spec. The SIG will sponsor a formal gathering to test medium-rate products in February.

"I predict that within two years of the spec being released, three-quarters of the Bluetooth products shipped will be using it," said Janson of CSR. The company's existing BlueCore3 products will support the spec with a firmware upgrade, he added.

Beyond that, the SIG is discussing a high-rate version of Bluetooth that buses 4 million rather than 1 million symbols/second, to potentially deliver up to 8 Mbits/s.

Separately, the SIG has a quality-of-service mechanism far along in development that could help multimedia devices gain needed access to bandwidth. The QoS scheme could be used with any data rate or audio scheme and is expected to be complete in time for inclusion in the next version of the spec.

Cell phones go blue

Several backers expressed optimism that the core Bluetooth technology, which has been widely overhyped, is finally starting to catch on. Nokia is launching 18 products using Bluetooth this year, 10 to 15 percent of Motorola's phones will be equipped with Bluetooth by the end of next year, and IBM and Toshiba are increasing the number of their notebook PC models using Bluetooth, according to representatives of the companies here.

"We foresee shipping in excess of tens of millions of phones using Bluetooth in 2004," said Steve Deutscher, director of product management for phone peripherals at Motorola Inc. "A year ago I would have said I don't know about the future of Bluetooth, but we are finally at the point now where we can see this getting into mass-market products."

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International Data Corp. (Framingham, Mass.) estimates 29 million Bluetooth chips shipped in 2002, soaring to 637 million in 2007. By that time as many as 65 percent of all cellular handsets, 44 percent of PDAs and 36 percent of notebooks could have Bluetooth built in, according to IDC.

The market watcher projects the average selling price of Bluetooth chips will fall from $4.75 this year to $3.45 in 2004 and $2.30 in 2007. Based on price declines for chips and batteries, one headset maker said it will ship by June a $59 Bluetooth headset, down from $99 today.